Some electronic devices such as smart phones include speakers. The electronic device includes an audio amplifier and other electronics that generate electrical signals to be provided to the speaker for conversion to audio. The audio amplifier is a power amplifier that amplifies low-power audio signals (e.g., signals comprising primarily frequencies between 20 Hz and 20 KHz) to a level suitable for driving a speaker. Audio amplifiers may be employed in the final stage of an audio playback chain to amplify audio signals for playback on a speaker which may comprise a headset or a speaker in a mobile device such as smart phone. Audio amplifiers may be implemented using class-D amplifiers, class AB amplifiers, and the like.
In some implementations, the voltage and/or current to the speaker is sensed, rescaled, and digitized as a feedback signal. The speaker voltage/current signals may be used to compute, for example, the speaker's coil temperature and excursion.